Show info when logging in

[dxlbnl]

Expected Behavior

When nerd is logging in (directly running nerd login) It's unclear the cli is trying to open a browser, in several cases (#310, #338, #150) it might not work at all, depending on the environment

Actual Behavior

Currently nothing is being shown

Preferred Behavior

Show a message stating something in the spirit of:

We've openend a browser page, if it doesn't show go to {url} instead. In order to login on a headless machine go to {doc_url}